1. Field of the Invention
This invention relates generally to a corona discharge igniter for receiving a voltage from a power source and emitting an electrical field for ionizing and igniting a mixture of fuel and air of an internal combustion engine, and methods of manufacturing the same.
2. Description of the Prior Art
An igniter of a corona discharge ignition system receives a voltage from a power source and emits an electrical field that forms a corona to ionize a mixture of fuel and air of an internal combustion engine. The igniter includes an electrode body portion extending longitudinally form an electrode terminal end to an electrode firing end. An insulator is disposed along the electrode body portion, and a shell is disposed along the insulator from an upper shell end to a lower shell end. The lower shell end faces toward the electrode firing end. The shell includes a lip at the upper shell end, in an area of the igniter known as a rollover region.
The electrode terminal end receives the voltage from the power source and the electrode firing end emits the electrical field that forms the corona. The electrical field includes at least one streamer, and typically a plurality of streamers forming the corona. The corona igniter does not include any grounded electrode element in close proximity to the electrode firing end. Rather, the mixture of air and fuel is ignited along the entire length of the high electrical field generated from the electrode firing end. An example of the igniter is disclosed in U.S. Patent Application Publication No. US 2010/0083942 to the present inventors, Lykowski and Hampton.
For internal combustion engine applications, it is desirable to concentrate the electrical field emissions at the electrode firing end. However, as shown in Prior Art FIG. 2, some electrical field emissions often occur in the rollover region, for example in the air surrounding the lip of the shell. These electrical field emission are referred to as arcing, or irregular corona, which is undesirable for many internal combustion engine applications. The irregular corona or arcing can degrade the quality of the ignition of the mixture of fuel and air.